Be like water
Lee believed that martial systems should be as flexible as possible. He often used water as an analogy for describing why flexibility is a desired trait in martial arts. Water is infinitely flexible. It can be seen through, and yet at other times it can obscure things from sight. It can split and go around things, rejoining on the other side, or it can crash through things. It can erode the hardest rocks by gently lapping away at them or it can flow past the tiniest pebble. Lee believed that a martial system should have these attributes.
Economy of motion
JKD students are told to waste no time or movement. When it comes to combat JKD practitioners believe the simplest things work best. Economy of motion is the principle by which JKD practitioners achieve "efficiency" describe in the three parts of JKD. Utilizing this principle conserves both energy and time. Energy and time are two crucial components in a physical confrontation that often leads to success if employed efficiently. In combat situations maximizing one's energy is beneficial in maintaining physical activity. Likewise minimizing the time to execute techniques because of traveling less distance is beneficial in that the opponent has less time to react
Stop hits & stop kicks
This means intercepting an opponent's attack with an attack of your own instead of a simple block. JKD practitioners believe that this is the most difficult defensive skill to develop. This strategy is a feature of some traditional Chinese martial arts, as well as an essential component of European épée fencing (known in fencing terminology as the "counter-attack"). Stop hits & kicks utilizes the principle of economy of motion by combining attack and defense into one movement thus minimizing the "time" element.
No high kicks
JKD practitioners believe they should target their kicks to their opponent's shins, knees, thighs, and mid section. These targets are the closest to the foot, provide more stability and are more difficult to defend against. However, as with all other JKD principles nothing is "written in stone". If a target of opportunity presents itself, even a target above the waist, one could take advantage of the situation without feeling hampered by this principle. Maintaining low kicks utilizes the principle of economy of motion by reducing the distance a kick must travel thus minimizing the "time" element. Low kicks are also more difficult to detect and thus guard against
Jeet Kune Do not only advocates the combination of aspects of different styles, it also can change many of those aspects that it adopts to suit the abilities of the practitioner. Additionally, JKD advocates that any practitioner be allowed to interpret techniques for themselves, and change them for their own purposes. For example, Lee almost always chose to put his power hand in the "lead," with his weaker hand back, within this stance he used elements of Boxing, Fencing and Wing Chun. Just like fencing, he labeled this position the "On Guard" position. Lee incorporated this position into his JKD as he felt it provided the best overall mobility. Lee felt that the dominant or strongest hand should be in the lead because it would perform a greater percentage of the work. Lee minimized the use of other stances except when circumstances warranted such actions. Although the On-Guard position is a good overall stance, it is by no means the only one. Lee acknowledged that there were times when other positions should be utilized.